MAVLink: use enum ap_message and remove unused param argument

saves us another 200 bytes of text

ArduPlane/GCS.h

@@ -56,7 +56,7 @@ public:
 	/// @param	id			ID of the message to send.
 	/// @param	param		Explicit message parameter.
 	///
-	void		send_message(uint8_t id, int32_t param = 0) {}
+	void		send_message(enum ap_message id) {}
 
 	/// Send a text message.
 	///
@@ -140,7 +140,7 @@ public:
 	GCS_MAVLINK(AP_Var::Key key);
 	void    update(void);
 	void	init(FastSerial *port);
-	void	send_message(uint8_t id, uint32_t param = 0);
+	void	send_message(enum ap_message id);
 	void	send_text(uint8_t severity, const char *str);
 	void	send_text(uint8_t severity, const prog_char_t *str);
 	void	acknowledge(uint8_t id, uint8_t sum1, uint8_t sum2);

ArduPlane/GCS_Mavlink.pde

@@ -139,7 +139,7 @@ GCS_MAVLINK::data_stream_send(uint16_t freqMin, uint16_t freqMax)
 }
 
 void
-GCS_MAVLINK::send_message(uint8_t id, uint32_t param)
+GCS_MAVLINK::send_message(enum ap_message id)
 {
     mavlink_send_message(chan,id, packet_drops);
 }

ArduPlane/Mavlink_Common.h

@@ -291,7 +291,7 @@ static void NOINLINE send_current_waypoint(mavlink_channel_t chan)
 
 
 // try to send a message, return false if it won't fit in the serial tx buffer
-static bool mavlink_try_send_message(mavlink_channel_t chan, uint8_t id, uint16_t packet_drops)
+static bool mavlink_try_send_message(mavlink_channel_t chan, enum ap_message id, uint16_t packet_drops)
 {
     int payload_space = comm_get_txspace(chan) - MAVLINK_NUM_NON_PAYLOAD_BYTES;
 
@@ -395,13 +395,13 @@ static bool mavlink_try_send_message(mavlink_channel_t chan, uint8_t id, uint16_
 
 #define MAX_DEFERRED_MESSAGES MSG_RETRY_DEFERRED
 static struct mavlink_queue {
-    uint8_t deferred_messages[MAX_DEFERRED_MESSAGES];
+    enum ap_message deferred_messages[MAX_DEFERRED_MESSAGES];
     uint8_t next_deferred_message;
     uint8_t num_deferred_messages;
 } mavlink_queue[2];
 
 // send a message using mavlink
-static void mavlink_send_message(mavlink_channel_t chan, uint8_t id, uint16_t packet_drops)
+static void mavlink_send_message(mavlink_channel_t chan, enum ap_message id, uint16_t packet_drops)
 {
     uint8_t i, nextid;
     struct mavlink_queue *q = &mavlink_queue[(uint8_t)chan];